US7340126B2 - Wavelength selective optical switch - Google Patents

Wavelength selective optical switch Download PDF

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US7340126B2
US7340126B2 US11/319,643 US31964305A US7340126B2 US 7340126 B2 US7340126 B2 US 7340126B2 US 31964305 A US31964305 A US 31964305A US 7340126 B2 US7340126 B2 US 7340126B2
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monitor
signal light
wavelength
input port
signal
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US20060215955A1 (en
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Nobuaki Mitamura
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Fujitsu Ltd
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Fujitsu Ltd
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/35—Optical coupling means having switching means
    • G02B6/3586—Control or adjustment details, e.g. calibrating
    • G02B6/3588—Control or adjustment details, e.g. calibrating of the processed beams, i.e. controlling during switching of orientation, alignment, or beam propagation properties such as intensity, size or shape
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
    • G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
    • G02B6/29304—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by diffraction, e.g. grating
    • G02B6/29305—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by diffraction, e.g. grating as bulk element, i.e. free space arrangement external to a light guide
    • G02B6/2931—Diffractive element operating in reflection
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
    • G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
    • G02B6/29379—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means characterised by the function or use of the complete device
    • G02B6/29395—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means characterised by the function or use of the complete device configurable, e.g. tunable or reconfigurable
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/35—Optical coupling means having switching means
    • G02B6/351—Optical coupling means having switching means involving stationary waveguides with moving interposed optical elements
    • G02B6/3512—Optical coupling means having switching means involving stationary waveguides with moving interposed optical elements the optical element being reflective, e.g. mirror
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/35—Optical coupling means having switching means
    • G02B6/354—Switching arrangements, i.e. number of input/output ports and interconnection types
    • G02B6/3554—3D constellations, i.e. with switching elements and switched beams located in a volume
    • G02B6/3556—NxM switch, i.e. regular arrays of switches elements of matrix type constellation
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/35—Optical coupling means having switching means
    • G02B6/354—Switching arrangements, i.e. number of input/output ports and interconnection types
    • G02B6/356—Switching arrangements, i.e. number of input/output ports and interconnection types in an optical cross-connect device, e.g. routing and switching aspects of interconnecting different paths propagating different wavelengths to (re)configure the various input and output links

Definitions

  • the present invention relates to a wavelength selective optical switch for branching a signal light of arbitrary wavelengths for each wavelength at a node in a large-scale photonic network to which a plurality of wavelength division multiplexing networks is connected.
  • a function of selecting to switch a particular wavelength from one fiber has been treated as important as a function of the optical switching, and a switching device for realizing such a function is called a wavelength selective optical switch.
  • a wavelength selective optical switch there are for example, a wavelength selective optical router for controlling and routing signal lights of individual wavelengths from an input fiber to an output fiber, a wavelength selective optical node bypass for controlling to bypass the particular wavelength from one fiber to an alternate fiber, a wavelength selective add/drop for controlling the adding/dropping of the particular wavelength to/from one fiber.
  • FIG. 23 is a perspective view of the conventional wavelength selective optical switch
  • FIG. 24 is a top view thereof
  • FIG. 25 is a side view from A-direction of FIG. 24 .
  • This conventional wavelength selective optical switch realizes the above described wavelength selective optical switch function, based on the operational principle in which parallel signal lights (collimate beams) of different wavelengths of M in number, which are emitted from the signal light input port 1 , are separated to different angular directions by the diffraction grating 5 , and thereafter, are condensed on different positions by the lens 6 (refer to FIG. 23 and FIG. 24 ), and the respective optical beams are reflected at desired angles by the mirror array 7 consisting of the M micro-mirrors 8 having angles variable due to the electrostatic attraction or the like, which are arranged on condensing positions of the respective optical beams passed through the lens 6 , to be led to desired signal light output ports 2 (refer to FIG. 23 and FIG. 25 ).
  • the respective micro-mirrors 8 of the mirror array 7 need to be angularly adjusted so that the optical beams return the desired signal light output ports 2 . Therefore, there has been conventionally used, for example, a method of detecting the angles of respective micro-mirrors 8 with the capacitance or the like to perform a feedforward control, a method of performing a feedback control so that the output intensity at the signal light output port for the desired wavelength becomes maximum, or the like.
  • the latter feedforward control there is a problem in that the micro-mirrors 8 cannot retain optimum angles if the capacitance is changed with time. Therefore, the latter feedback control is generally used.
  • the wavelength selective optical switch In the case where the wavelength selective optical switch is operated in the actual network, such a case where signal lights of all reactive wavelengths (channels) are necessarily operated from an initial stage of the service-in is rare. As shown in an optical path indicated by the broken line in FIG. 24 , there are many cases where the wavelength which is not in the service-in (dark channel) exists. In such a case, even when the signal light of the wavelength which has not been in service-in is newly in the service-in, the wavelength selective optical switch needs to appropriately start the switching operation without the interference or the crosstalk. Further, in the applications such as the wavelength selective optical router and the like, there is a case where the wavelengths or the number of wavelengths of the signal lights input to the wavelength selective optical router are frequently changed according to the switching status of routes. Even in such a case, needless to say, the wavelength selective optical router needs to operate without the interference or the crosstalk.
  • FIG. 26 is a side view similar to FIG. 25 , and shows by the broken line a route passing the micro-mirror 8 corresponding to the dark channel under the above status.
  • the present invention has been accomplished in view of the above problems and has an object to provide a wavelength selective optical switch with a simple configuration, capable of reliably controlling an angle of a reflecting surface of a mirror corresponding to a wavelength through which a signal light is not input, and of avoiding the crosstalk when the signal light is newly input.
  • the present invention provides a wavelength selective optical switch which includes optical path switching means provided with a plurality of mirrors on which signal lights of respective wavelengths contained in a wavelength division multiplexed light are incident, for controlling angular variable reflecting surfaces of the respective mirrors to switch optical paths for the signal lights reflected by the respective mirrors to arbitrary directions for each wavelength, comprising: wavelength detecting means for detecting the wavelengths of the signal lights input to the optical path switching means; monitor light generating means for generating a monitor light for monitoring and controlling the reflecting surface angles of the plurality of mirrors, irrespectively of the wavelengths of the signal lights input to the optical path switching means; a monitor light input port to which the monitor light from the monitor light generating means is input; a monitor light output port to which the monitor light emitted from the monitor light input port and reflected by the respective mirrors of the optical path switching means is coupled; monitor light intensity detecting means for detecting the intensity of the monitor light output from the monitor light output port; and control means for feedback controlling, for the wavelength of
  • the reflecting surface angle of the corresponding mirror can be reliably controlled utilizing the monitor light.
  • the wavelength selective optical switch of the present invention as described in the above, with the simple configuration using the monitor light, even when the signal light which has not been input to the optical path switching means is newly input, it becomes possible to provide the wavelength selective optical switch which does not occur the crosstalk.
  • FIG. 1 is a schematic diagram showing the entire configuration of a first embodiment according to the present invention
  • FIG. 2 is a side view for explaining a configuration and an operation of a main body portion in the first embodiment
  • FIG. 3 is another side view for explaining an operation of the first embodiment
  • FIG. 4 is a further side view for explaining the operation of the first embodiment
  • FIG. 5 is a flowchart for explaining the operation of the first embodiment
  • FIG. 6 is a side view for explaining a configuration and an operation of a main body portion in a second embodiment according to the present invention.
  • FIG. 7 is another side view for explaining an operation of the second embodiment
  • FIG. 8 is a further side view for explaining the operation of the second embodiment
  • FIG. 9 is a side view for explaining a configuration and an operation of a main body portion in a third embodiment according to the present invention.
  • FIG. 10 is another side view for explaining an operation of the third embodiment
  • FIG. 11 is a further side view for explaining the operation of the third embodiment.
  • FIG. 12 is a side view for explaining a configuration and an operation of a main body portion in a fourth embodiment according to the present invention.
  • FIG. 13 is another side view for explaining an operation of the fourth embodiment
  • FIG. 14 is a further side view for explaining the operation of the fourth embodiment.
  • FIG. 15 is a top view for explaining a configuration and an operation of a main body portion in a fifth embodiment according to the present invention.
  • FIG. 16 is a side view showing the vicinity of each port in FIG. 15 from B-direction;
  • FIG. 17 is another top view for explaining an operation of the fifth embodiment.
  • FIG. 18 is a side view showing the vicinity of each port in FIG. 17 from B-direction;
  • FIG. 19 is a top view for explaining a configuration and an operation of a main body portion in a sixth embodiment according to the present invention.
  • FIG. 20 is a side view showing the vicinity of each port in FIG. 19 from B-direction;
  • FIG. 21 is another top view for explaining an operation of the sixth embodiment.
  • FIG. 22 is a side view showing the vicinity of each port in FIG. 21 from B-direction;
  • FIG. 23 is a perspective view showing a configuration example of a conventional wavelength selective optical switch
  • FIG. 24 is a top view for explaining an operation of the conventional wavelength selective optical switch
  • FIG. 25 is a side view of FIG. 24 from A-direction
  • FIG. 26 is another side view for explaining the operation of the conventional wavelength selective optical switch.
  • FIG. 27 is a further side view for explaining the operation of the conventional wavelength selective optical switch.
  • FIG. 1 is a schematic diagram showing the entire configuration of a first embodiment of a wavelength selective optical switch according to the present invention.
  • a wavelength selective optical switch in a first embodiment comprises, in addition to a signal light input port 1 to which a wavelength division multiplexed signal light is input and a plurality of signal light output ports 2 , a monitor light input port 10 to which a monitor light is input and a monitor light output port 11 from which the monitor light is output, as an input and output port configuration of a main body portion 9 basically provided with a configuration similar to that of the conventional wavelength selective optical switch shown in FIG. 23 .
  • the main body portion 9 includes a function as optical path switching means.
  • an internal light source 12 as monitor light generating means is connected via an optical fiber.
  • the internal light source 12 is disposed for monitoring and controlling angles of micro-mirrors independent of wavelengths of the monitor light input to the monitor light input port 10 .
  • a broadband white light source for example, LED, ASE or the like, is used as the internal light source 12 .
  • a monitor light intensity monitor 13 as monitor light intensity detecting means for monitoring the intensity of the monitor light output from the monitor light output port 11 is connected via the optical fiber to the monitor light output port 11 .
  • a wavelength detector 14 as wavelength detecting means for detecting the wavelengths of the signal lights input to the signal light input port 1 is connected via an optical branching device 16 1 , which is inserted onto the optical fiber between the signal light input port 1 and the main body portion 9 .
  • a plurality of optical spectrum monitors 15 for monitoring the spectrums of the signal lights respectively output from the plurality of signal light output ports 2 is connected via optical branching devices 16 2 which are inserted onto the optical fibers between the main body portion 9 and the respective signal light output ports 2 .
  • the wavelength selective optical switch in the present embodiment includes a control circuit 17 as control means capable of controlling, among the plurality of micro-mirrors 8 in the main body portion 9 (refer to FIG. 23 or FIG. 24 ), an angle of the one corresponding to a wavelength (dark channel) of a signal light which is not input to the signal light input port 1 , so that the intensity of the monitor light output from the monitor light output port 11 becomes maximum.
  • the control circuit 17 is electrically connected to the monitor light intensity monitor 13 , the wavelength detector 14 , the optical spectrum monitor 15 and the main body portion 9 , to perform, in the same way as in the conventional technology, a feedback control of the micro-mirrors 8 based on the intensity of the signal lights output from the respective signal light output ports 2 , in addition to an angle control of the micro-mirrors 8 based on the intensity of the monitor light.
  • the control of the micro-mirrors 8 by the control circuit 17 will be described later in detail.
  • FIG. 2 to FIG. 4 show a detailed configuration of the main body portion 9 in FIG. 1 .
  • FIG. 2 to FIG. 4 are side views of the configuration of the main body portion 9 from A-direction (refer to FIG. 24 ).
  • the diffraction grating 5 and the micro-mirrors 8 are installed with respect to the lens 6 , on positions of substantial focal distance f of the lens 6 .
  • the signal light input port 1 , the monitor light output port 11 , the plurality of signal light output ports 2 and the monitor light input port 10 are arranged on a straight line in this order, so that, when the signal lights emitted from the signal light input port 1 are reflected by the micro-mirrors 8 which are feedback controlled according to the output intensity of the monitor light from the monitor light output port 11 , reflected lights of the signal lights are not coupled to the plurality of signal light output ports 2 , and also, so that, when the monitor light emitted from the monitor light input port 10 is reflected by the micro-mirrors 8 which are feedback controlled according to the output intensity of the signal lights from the signal light output ports 2 , reflected lights of the monitor light are neither coupled to the signal light input port 1 nor the plurality of signal light output ports 2 .
  • each port arrangement may be made in reverse to the above order.
  • the space between each port is desirable to be narrowed in order to reduce an angular movable range of each micro-mirror 8 .
  • the space between each port is made narrow to the extent possible, and also, each port is arranged at substantially even spaces.
  • a method of selectively outputting the signal lights of respective wavelengths (sometimes, to be referred to as wavelength signal lights, hereunder), which are input to the signal light input port 1 , from desired signal light output ports 2 is similar to that in the conventional wavelength selective optical switch described in the above.
  • this method will be described step by step in the following, while appropriately referring to FIG. 23 and FIG. 24 described in the above, since such a description is helpful for understanding the function and effect of the present wavelength selective optical switch.
  • the wavelength signal lights of M in number are input to the optical fiber 4 of the signal light input port 1 , and a light emitted from the optical fiber 4 becomes a parallel optical beam (collimated beam) by the collimate lens 3 .
  • the wavelength signal lights of M in number being one parallel beam are diffracted to be separated to different angle directions (horizontal direction in FIG. 23 ) according to the wavelengths by the reflective type diffraction grating 5 , and are divided Into a plurality of parallel beams whose traveling directions (angles) are different from each other ( FIG. 23 and FIG. 24 ).
  • the M wavelength signal lights whose traveling directions (angles) are different from each other are condensed by the lens 6 on different portions (positions deviated to the horizontal direction in FIG. 23 ).
  • the M wavelength signal lights are condensed while being deviated in parallel to each other ( FIG. 24 ).
  • the respective wavelength signal lights are condensed while being aligned at substantially equal intervals.
  • the wavelength spacing is not equal.
  • the spacing between each optical beam divided according to the wavelength is not equal, the spaces between the condensing positions of the wavelength signal lights are slightly deviated.
  • the M wavelength signal lights are reflected independently at desired angles in a vertical direction in FIG. 23 , by the M angle variable micro-mirrors 8 arranged on the condensing positions of the wavelength signal lights.
  • an angle between the optical beam and the micro-mirror 8 when viewed from above in FIG. 23 is made perpendicular to each other. Namely, when viewed from above in FIG. 23 , it seems that the optical beams incident on the micro-mirrors 8 are reflected to the exactly same direction to return ( FIG. 24 ).
  • the angles of the micro-mirrors 8 are set to be equiangular and also to be variable in up to N stages same as the number of the signal light output ports 2 .
  • the micro-mirror 8 is given with the predetermined electric power, to present a predetermined angle.
  • the respective optical beams reflected by the micro-mirrors 8 are returned to the lens 6 , and again becomes the parallel beam ( FIG. 23 ).
  • the micro-mirrors 8 are installed on the positions of substantial focal distance f of the lens 6 , the optical beams of up to N in number reflected according to the angles of the micro-mirrors 8 are deviated in parallel to the vertical direction in FIG. 23 .
  • the angles of the micro-mirrors 8 are set to be equiangular and to be variable in stepwise, deviations of the optical beams in the vertical direction are at equal spacing.
  • the optical beams of up to N in number deviated at equal spacing in the vertical direction in FIG. 23 again return to the diffraction grating 5 .
  • the respective optical beams are again incident on the diffraction grating 5 at angles same as the angles (angles in the horizontal direction in FIG. 23 ) at which the optical beams have been emitted from the diffraction grating 5 on an outward route. Therefore, the respective optical beams are diffracted while being deviated at equal spacing in the vertical direction in FIG. 23 , to directions (angles) same as the directions (angles) of when the optical beams have been incident on the diffraction grating 5 from the signal light input port 1 on the outward route ( FIG. 24 ). Then, the optical beams passed through the diffraction grating 5 are respectively coupled to the optical fiber 4 via the collimate lenses 3 aligned at even spaces in the vertical direction in FIG. 23 , to be respectively output from the N signal light output ports 2 .
  • the present wavelength selective optical switch is capable of selectively outputting the wavelength signal lights input to the signal light input port 1 , from the desired signal light output ports 2 according to the angles of the micro-mirrors 8 .
  • the wavelengths of the signal lights input to the signal light input port 1 are detected by the wavelength detector 14 connected to the signal light input port 1 via the optical branching device 16 1 , and based on a detection result, the control circuit 17 gains the information relating to the wavelengths of the signal lights which are input to the signal light input port 1 and a wavelength of a signal light which is not input to the signal light input port 1 (S 1 in FIG. 5 ).
  • the intensity of the wavelength signal lights which are input to the signal light input port 1 is detected by the respective optical spectrum monitors 15 respectively connected to the signal light output ports 2 via the optical branching devices 16 2 .
  • the control circuit 17 feedback controls the angles of the micro-mirrors 8 corresponding to the respective wavelengths so that the output intensity of the respective wavelengths in the desired signal light output ports 2 becomes a predetermined value or maximum, and the feedback controlled angles of the micro-mirrors are maintained (S 2 in FIG. 5 ).
  • the control circuit 17 gains the wavelength of the signal light which is not input to the signal light input port 1 , which micro-mirror 8 on the mirror array 7 should be controlled, can be judged by the control circuit 17 .
  • the angles of the micro-mirrors 8 are controlled so that a particular wavelength signal light input to the signal light input port 1 is coupled to the fifth signal light output port 2 from the top.
  • the monitor light from the internal light source 12 reaches the micro-mirrors 8 via the monitor light input port 10 , the diffraction grating 5 and the lens 6 .
  • the control circuit 17 can control the angle of the micro-mirror 8 corresponding to the dark channel to maintain the micro-mirror 8 at a particular angle, so that the output intensity in the monitor light output port 11 becomes maximum (S 3 in FIG. 5 ).
  • the monitor light intensity monitor 13 is an optical spectrum monitor, it is easy to feedback control the angles of the micro-mirrors 8 corresponding to the plurality of dark channels independently and simultaneously, by a plurality of control circuits. Further, even if the monitor light intensity monitor 13 is an optical intensity monitor, such as a single PD element, for detecting the intensity of all wavelengths independent of the wavelengths, the angles of the micro-mirrors 8 corresponding to the plurality of dark channels may be sequentially feedback controlled, so that the total optical intensity detected by the optical intensity monitor becomes maximum. In this case, since an expensive optical spectrum monitor does not need to be particularly used, it becomes possible to realize the wavelength selective optical switch of lower cost.
  • the broadband white light source is used as the internal light source 12 , the light in the whole wavelength region (strictly speaking, the total range of a band of the white light source) is split by the diffraction grating 5 , and the monitor light reaches all of the micro-mirrors 8 . Therefore, it is possible to feedback control all of the micro-mirrors 8 according to the output intensity of the monitor light.
  • FIG. 2 shows one example of a status where the micro-mirror 8 corresponding to the dark channel is feedback controlled according to the output intensity of the monitor light, in which the angle of the micro-mirror 8 is controlled so that the monitor light input to the monitor light input port 10 is coupled to the monitor light output port 11 .
  • the monitor light since the broadband white light source is used as the internal light source 12 , the monitor light reaches all the micro-mirrors 8 . Therefore, it becomes necessary that the monitor light for the wavelengths of the signal lights which are originally input to the signal light input port 1 is neither coupled to the signal light input port 1 nor the signal light output ports 2 . With regard to this, as shown in FIG. 4 , in the arrangement of each port in the present wavelength selective optical switch, since the monitor light reflected by the micro-mirrors 8 which are feedback controlled according to the intensity of the signal lights coupled to the signal light output ports 2 , reaches above the signal light input port 1 , the monitor light is not coupled to any port.
  • the broadband white light source is used as the internal light source 12 .
  • a light source capable of emitting only a light of particular wavelength for example, a wavelength variable laser light source, a wavelength variable light source made up by combining the broadband white light source and a wavelength variable filter or the like, as the internal light source 12 .
  • the monitor light is output from the internal light source 12 only for the wavelength of the signal light which is not input to the signal light input port 1 , the monitor light is neither coupled to the signal light input port 1 nor the signal light output ports 12 .
  • the broadband white light source whose cost is lower than the wavelength variable laser light source or the like, as the internal light source 12 .
  • the control circuit 17 suspends the above described feedback control according to the output intensity of the monitor light for the micro-mirror 8 corresponding to the new wavelength detected by the wavelength detector 14 , and sets the angle of the corresponding micro-mirror 8 at an initial value corresponding to the signal light output port 2 which is the determination of the new wavelength signal light, and thereafter, performs the feedback control according to the output intensity of the signal light coupled to this signal light output port 2 (S 5 in FIG. 5 ).
  • the control circuit 17 sets the angle of the corresponding micro-mirror 8 at an initial value corresponding to the signal light output port 2 which is the new determination, and thereafter, performs the feedback control according to the output intensity of the signal light coupled to this signal light output port 2 (S 6 in FIG. 5 ).
  • the control circuit 17 suspends the feedback control for the micro-mirror 8 corresponding to the wavelength according to the output intensity of the signal light, to switch the control to the feedback control according to the output intensity of the monitor light (S 8 in FIG. 5 ).
  • the above described operation in the case where the signal light is not input to the signal light input port 1 is repetitively performed (S 3 to S 5 in FIG. 5 ).
  • the wavelength selective optical switch in the first embodiment it becomes possible to more reliably avoid, with a simple configuration, the crosstalk which conventionally has a possibility to occur when the new wavelength signal light is input.
  • FIG. 6 to FIG. 8 are side views showing a configuration of a main part of the wavelength selective optical switch in the second embodiment. Note, the entire configuration of the present wavelength selective optical switch is similar to that in the first embodiment shown in FIG. 1 , and therefore, the description thereof is omitted.
  • the present wavelength selective optical switch is made up by making-the spatial arrangement of each port in the first embodiment different.
  • the configuration other than the arrangement of each port is similar to that in the first embodiment.
  • the monitor light output port 11 , the monitor light input port 10 , the plurality of signal light output ports 2 and the signal light input port 1 are arranged at substantially even spaces on a straight line in this order.
  • each port in the second embodiment the angular movable range of each micro-mirror 8 becomes twice the angular movable range in the first embodiment. Therefore, from the view point that the angular movable range of each micro-mirror 8 is narrowed to suppress the drive electricity for the micro-mirrors 8 , and the switching operation of optical paths is accelerated, the configuration in the first embodiment is more advantageous than that in the second embodiment.
  • FIG. 9 to FIG. 11 are side views showing a configuration of a main part of the wavelength selective optical switch in the third embodiment. Note, the entire configuration of the present wavelength selective optical switch is similar to that in the first embodiment shown in FIG. 1 , and therefore, the description thereof is omitted.
  • the present wavelength selective optical switch is made up by making the spatial arrangement of each port in the first or second embodiment different.
  • the configuration other than the arrangement of each port is similar to that in the first or second embodiment.
  • the signal light input port 1 , the monitor light input port 10 , the plurality of signal light output ports 2 and the monitor light output port 11 are arranged on a straight line in this order.
  • each port in the case where each port is arranged at even spaces and also the broadband white light source is used as the internal light source 12 , the monitor light for the wavelength of the signal light input to the signal light input port 1 , which is reflected by the micro-mirror 8 feedback controlled according to the signal light output intensity, is coupled to the signal light input port 1 and the signal light output port 2 .
  • the plurality of signal light output ports 2 is arranged at substantially even spaces, and also, the signal light input port 1 and the monitor light input port 10 are arranged on a straight line at the space which is different from the integral multiple of the arrangement space of each signal light output port 2 .
  • the space between the signal light input port 1 and the monitor light input port 10 is set to be about 1.5 times of the arrangement space of each signal light output port 2 .
  • the monitor light in order to avoid the coupling of the monitor light to the signal light input port 1 and the signal light output port 2 , it is also possible to emit from the internal light source 12 the monitor light only for the wavelength of the signal light which is not input to the signal light input port 1 , using for example the wavelength variable laser light source or the wavelength variable light source made up by combining the broadband white light source and the wavelength variable filter as the internal light source 12 , as described in the above, in place of the application of the above port arrangement.
  • the avoidance measure in which the arrangement of each port is devised as shown in the present embodiment is advantageous in cost performance, since it is possible to use the broadband white light source whose cost is lower than the wavelength variable laser light source or the like.
  • the monitor light for the wavelength of the signal light input to the signal light input port 1 which is reflected by the micro-mirror 8 feedback controlled according to the signal light output intensity, reaches just the intermediate position between the third and fourth signal light output ports 2 from the top, and therefore, is hardly coupled to the signal light output port 2 . Accordingly, any practical issue does not occur.
  • the wavelength signal light newly input to the signal light input port 1 is not coupled to any port. Therefore, even if the new wavelength signal light is input, the crosstalk does not occur.
  • each port in the third embodiment since the angular movable range of each micro-mirror 8 is slightly broader than that in the first embodiment. Therefore, from the view point of the angular movable range of the micro-mirror, the configuration in the first embodiment is more advantageous than that in the third embodiment.
  • FIG. 12 to FIG. 14 are side views showing a configuration of a main part of the wavelength selective optical switch in the fourth embodiment. Note, the entire configuration of the present wavelength selective optical switch is similar to that in the first embodiment shown in FIG. 1 , and therefore, the description thereof is omitted.
  • the present wavelength selective optical switch is made up by making the spatial arrangement of each port in each of the first to third embodiments different.
  • the configuration other than the arrangement of each port is similar to that in each of the first to third embodiments.
  • the monitor light output port 11 , the monitor light input port 10 , the signal light input port 1 and the plurality of signal light output port 2 are arranged on a straight line in this order.
  • the space between the signal light input port 1 and the monitor light input port 10 is set to be about 1.5 times of the arrangement space of each signal light output port 2 .
  • each port as apparent from an optical path for the dark channel indicated by the broken line in FIG. 12 and an optical path for the reflected light of the signal light indicated by the solid line in FIG. 13 , since the wavelength signal light newly input to the signal light input port 1 is not coupled to any port, the crosstalk does not occur even if the new wavelength signal light is input. Further, as apparent from an optical path for the reflected light of the monitor light indicated by the solid line in FIG.
  • the monitor light for the signal light input to the signal light input port 1 which is reflected by the micro-mirror 8 feedback controlled according to the signal light output intensity, reaches just the intermediate position between the second and third signal light output ports 2 from the top, and therefore, is hardly coupled to the signal light output port 2 . Accordingly, the practical issue does not occur.
  • the configuration in the first or third embodiment is more advantageous than that in the fourth embodiment.
  • FIG. 15 and FIG. 17 are top views showing a configuration of a main part of the wavelength selective optical switch in the fifth embodiment.
  • FIG. 16 and FIG. 18 are side views of a configuration of the vicinity of each port of FIG. 15 and FIG. 17 viewed from B-direction. Note, the entire configuration of the present wavelength selective optical switch is similar to that in the first embodiment shown in FIG. 1 , and therefore, the description thereof is omitted.
  • the present wavelength selective optical switch is made up by making the spatial arrangement of each port in each of the first to fourth embodiments different.
  • the configuration other than the arrangement of each port is similar to that in each of the first to fourth embodiments.
  • the signal light input port 1 and the plurality of signal light output ports 2 are arranged on a straight line “a”, and the monitor light input port 10 and the monitor light output port 11 are arranged on a straight line “b” orthogonal to the straight line “a”.
  • the monitor light input port 10 and the monitor light output port 11 are arranged so that the intersection “c” is located on the opposite side to the signal light input port 1 from the intermediate position of the plurality of signal light output ports 2 ( FIG. 16 ).
  • the micro-mirror 8 corresponding to the wavelength of the signal light which is not input to the signal light input port 1 is feedback controlled so that the output intensity of the monitor light which is coupled to the monitor light output port 11 (solid line in FIG. 15 ) becomes maximum. Then, when the signal light which has not been input to the signal light input port 1 is newly input, the reflected light of this signal light by the above micro-mirror 8 is deviated below the plurality of the signal light output ports 2 , as indicated by the broken-lined circle on the bottom side in FIG. 16 . Therefore, even if the new wavelength signal light is input, the crosstalk does not occur.
  • the monitor light for the wavelength of the signal light input to the signal light input port 1 which is reflected by the micro-mirror 8 feedback controlled according to the signal light output intensity (for example, the micro-mirror positioned on the top (the rightmost to the lens 6 ) of the plurality of micro-mirrors to which the light is radiated in FIG. 17 ), is deviated from the straight line “a” as indicated by the broken-lined circle on the left middle in FIG. 18 . Therefore, the monitor light corresponding to the wavelength of the signal light input to the signal light input port 1 is neither coupled to the signal light input port 1 nor the signal light output ports 2 .
  • each port are two-dimensionally arranged, compared to the first to fourth embodiments, the adjustment of each port is slightly difficult.
  • the size in the direction of the straight line “a” on which the signal light input port 1 and the plurality of signal light output ports 2 are arranged can be made smaller than that in each of the first to fourth embodiment.
  • FIG. 19 and FIG. 21 are top views showing a configuration of a main part of the wavelength selective optical switch in the sixth embodiment.
  • FIG. 20 and FIG. 22 are side views of a configuration of the vicinity of each port of FIG. 19 and FIG. 21 viewed from B-direction. Note, the entire configuration of the present wavelength selective optical switch is similar to that in the first embodiment shown in FIG. 1 , and therefore, the description thereof is omitted.
  • the present wavelength selective optical switch is made up by making the spatial arrangement of each port in each of the first to fifth embodiments different.
  • the configuration other than the arrangement of each port is similar to that in each of the first to fifth embodiments.
  • the signal light input port 1 and the plurality of signal light output ports 2 are arranged on a straight line “a”, and the monitor light input port 10 and the monitor light output port 11 are arranged on a straight line “b” orthogonal to the straight line “a”.
  • the arrangement up to this is similar to that in the above described fifth embodiment.
  • the difference of the sixth embodiment from the fifth embodiment is in that the position of the intersection “c” when the intersection of the straight lines “a” and “b” is “c”, is arranged on the outer side of the signal light input port 1 and the plurality of signal light output ports 2 .
  • the monitor light input port 10 and the monitor light output port 11 are arranged so that the intersection “c” is located above the signal light input port 1 arranged on the top.
  • the micro-mirror 8 corresponding to the wavelength of the signal light which is not input to the signal light input port 1 is feedback controlled so that the output intensity of the monitor light which is coupled to the monitor light output port 11 (solid line in FIG. 19 ) becomes maximum. Then, when the signal light which has not been input to the signal light input port 1 is newly input, this signal light is deviated above on the opposite side to the plurality of the signal light output ports 2 as indicated by the broken-lined circle on the upper side of FIG. 20 . Therefore, even if the new wavelength signal light is input, the crosstalk does not occur.
  • the monitor light for the wavelength of the signal light input to the signal light input port 1 which is reflected by the micro-mirror 8 feedback controlled according to the signal light output intensity (for example, the micro-mirror positioned on the top (the rightmost to the lens 6 ) of the plurality of micro-mirrors to which the light is radiated in FIG. 21 ), is deviated from the straight line “a” as indicated by the broken-lined circle on the left middle in FIG. 22 . Therefore, the monitor light corresponding to the wavelength of the signal light input to the signal light input port 1 is neither coupled to the signal light input port 1 nor the signal light output ports 2 .
  • the wavelength detector 14 which is commonly used in the first to sixth embodiments, it is possible to use an optical spectrum monitor comprising a spectral element for separating the light input to the signal light input port 1 for each wavelength and a light receiving element array for receiving the, lights of respective wavelengths separated by the spectral element, an optical spectrum monitor comprising a wavelength variable filter for extracting a particular wavelength and a light receiving element for receiving the light extracted from the wavelength variable filter, or the like. Further, even in the case where the optical spectrum monitor is used as the monitor light intensity monitor 13 , it is possible to use the one similar to the specific configuration of the wavelength detector 14 .
  • the signal light input port 1 is arranged on the outer side of the plurality of signal light output ports 2 .
  • the plurality of signal light output ports 2 is often subjected to the collective optical axis adjustment. Therefore, in view of the facility of optical axis adjustment, the port arrangement in the first to sixth embodiments is advantageous.
  • the wavelength selective optical switch of the present invention is not limited to the one in each of the first to sixth embodiments, and it is apparent that the person skilled in the art can modify the wavelength selective optical switch within a range defined in claims and within a range of the equivalence thereof, based on the principle of the present invention.

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